I just bought a townhouse, and last weekend the furnace worked fine. Now, all that I get out of the registers is cool air. The furnace ran almost all night, but no warm air at all. What might the problem be?

My comfort maker furnace only blow cold air when it come on it don't lightup

I think you both need to go to the sticky at the top of the forum, https://www.askmehelpdesk.com/heating-air-conditioning/heating-cooling-maintenance-repair-troubleshooting-frequently-asked-questions-58313.html Use the info there to better identify your system and at what point it is failing. If you don't find the answer there, post back with more details.